/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.evaluation.value;

import proguard.classfile.ClassConstants;

/**
 * This class represents a partially evaluated instruction offset. It can contain 0 or more specific instruction
 * offsets. Each instruction offset can be flagged as an ordinary offset, a method parameter, a method return value, a
 * field value, a new instance value, or an exception handler.
 *
 * @author Eric Lafortune
 */
public class InstructionOffsetValue extends Category1Value {
    private static final int[] EMPTY_OFFSETS = new int[0];
    public static final InstructionOffsetValue EMPTY_VALUE = new InstructionOffsetValue(EMPTY_OFFSETS);

    public static final int INSTRUCTION_OFFSET_MASK = 0x01ffffff;
    public static final int METHOD_PARAMETER = 0x01000000; // Method parameter indices are not really instruction
                                                           // offsets.
    public static final int METHOD_RETURN_VALUE = 0x02000000;
    public static final int FIELD_VALUE = 0x04000000;
    public static final int NEW_INSTANCE = 0x08000000;
    public static final int CAST = 0x10000000;
    public static final int EXCEPTION_HANDLER = 0x20000000;

    private int[] values;

    /**
     * Creates a new InstructionOffsetValue with the given instruction offset.
     */
    public InstructionOffsetValue(int value) {
        this.values = new int[] {value};
    }

    /**
     * Creates a new InstructionOffsetValue with the given list of instruction offsets.
     */
    public InstructionOffsetValue(int[] values) {
        this.values = values;
    }

    /**
     * Returns the number of instruction offsets of this value.
     */
    public int instructionOffsetCount() {
        return values.length;
    }

    /**
     * Returns the specified instruction offset of this value.
     */
    public int instructionOffset(int index) {
        return values[index] & INSTRUCTION_OFFSET_MASK;
    }

    /**
     * Returns whether the given value is present in this list of instruction offsets.
     */
    public boolean contains(int value) {
        for (int index = 0; index < values.length; index++) {
            if (values[index] == value) {
                return true;
            }
        }

        return false;
    }

    /**
     * Returns the minimum value from this list of instruction offsets. Returns <code>Integer.MAX_VALUE</code> if the
     * list is empty.
     */
    public int minimumValue() {
        int minimumValue = Integer.MAX_VALUE;

        for (int index = 0; index < values.length; index++) {
            int value = values[index] & INSTRUCTION_OFFSET_MASK;

            if (minimumValue > value) {
                minimumValue = value;
            }
        }

        return minimumValue;
    }

    /**
     * Returns the maximum value from this list of instruction offsets. Returns <code>Integer.MIN_VALUE</code> if the
     * list is empty.
     */
    public int maximumValue() {
        int maximumValue = Integer.MIN_VALUE;

        for (int index = 0; index < values.length; index++) {
            int value = values[index] & INSTRUCTION_OFFSET_MASK;

            if (maximumValue < value) {
                maximumValue = value;
            }
        }

        return maximumValue;
    }

    /**
     * Returns whether the specified instruction offset corresponds to a method parameter.
     */
    public boolean isMethodParameter(int index) {
        return (values[index] & METHOD_PARAMETER) != 0;
    }

    /**
     * Returns the specified method parameter (assuming it is one).
     */
    public int methodParameter(int index) {
        return values[index] & ~METHOD_PARAMETER;
    }

    /**
     * Returns whether the specified instruction offset corresponds to a method return value.
     */
    public boolean isMethodReturnValue(int index) {
        return (values[index] & METHOD_RETURN_VALUE) != 0;
    }

    /**
     * Returns whether the specified instruction offset corresponds to a field value.
     */
    public boolean isFieldValue(int index) {
        return (values[index] & FIELD_VALUE) != 0;
    }

    /**
     * Returns whether the specified instruction offset corresponds to a new instance.
     */
    public boolean isNewinstance(int index) {
        return (values[index] & NEW_INSTANCE) != 0;
    }

    /**
     * Returns whether the specified instruction offset corresponds to a cast.
     */
    public boolean isCast(int index) {
        return (values[index] & CAST) != 0;
    }

    /**
     * Returns whether the specified instruction offset corresponds to an exception handler.
     */
    public boolean isExceptionHandler(int index) {
        return (values[index] & EXCEPTION_HANDLER) != 0;
    }

    /**
     * Returns an InstructionOffsetValue that contains the instructions offsets of this value and the given instruction
     * offset.
     */
    public InstructionOffsetValue add(int value) {
        if (contains(value)) {
            return this;
        }

        int[] newValues = new int[values.length + 1];
        System.arraycopy(values, 0, newValues, 0, values.length);
        newValues[values.length] = value;

        return new InstructionOffsetValue(newValues);
    }

    /**
     * Returns an InstructionOffsetValue that contains the instructions offsets of this value but not the given
     * instruction offset.
     */
    public InstructionOffsetValue remove(int value) {
        for (int index = 0; index < values.length; index++) {
            if (values[index] == value) {
                int[] newValues = new int[values.length - 1];
                System.arraycopy(values, 0, newValues, 0, index);
                System.arraycopy(values, index + 1, newValues, index, values.length - index - 1);

                return new InstructionOffsetValue(newValues);
            }
        }

        return this;
    }

    /**
     * Returns the generalization of this InstructionOffsetValue and the given other InstructionOffsetValue. The values
     * of the other InstructionOffsetValue are guaranteed to remain at the end of the list, in the same order.
     */
    public final InstructionOffsetValue generalize(InstructionOffsetValue other) {
        // If the values array of either is empty, we can return the other one.
        int[] thisValues = this.values;
        if (thisValues.length == 0) {
            return other;
        }

        int[] otherValues = other.values;
        if (otherValues.length == 0) {
            return this;
        }

        // Compute the length of the union of the arrays.
        int newLength = thisValues.length;
        for (int index = 0; index < otherValues.length; index++) {
            if (!this.contains(otherValues[index])) {
                newLength++;
            }
        }

        // If the length of the union array is equal to the length of the other
        // values array, we can return it.
        if (newLength == otherValues.length) {
            return other;
        }

        // If the length of the union array is equal to the length of this
        // values array, we can return it. We have to make sure that the other
        // values are at the end. We'll just test one special case, with a
        // single other value.
        if (newLength == this.values.length && otherValues.length == 1
            && thisValues[thisValues.length - 1] == otherValues[0]) {
            return this;
        }

        // Create the union array.
        int newIndex = 0;
        int[] newValues = new int[newLength];

        // Is the length of the union array is equal to the sum of the lengths?
        if (newLength == thisValues.length + otherValues.length) {
            // We can just copy all values, because they are unique.
            System.arraycopy(thisValues, 0, newValues, 0, thisValues.length);

            newIndex = thisValues.length;
        } else {
            // Copy the values that are different from the other array.
            for (int index = 0; index < thisValues.length; index++) {
                if (!other.contains(thisValues[index])) {
                    newValues[newIndex++] = thisValues[index];
                }
            }
        }

        // Copy the values from the other array.
        System.arraycopy(otherValues, 0, newValues, newIndex, otherValues.length);

        return new InstructionOffsetValue(newValues);
    }

    // Implementations for Value.

    public final InstructionOffsetValue instructionOffsetValue() {
        return this;
    }

    public boolean isSpecific() {
        return true;
    }

    public boolean isParticular() {
        return true;
    }

    public final Value generalize(Value other) {
        return this.generalize(other.instructionOffsetValue());
    }

    public final int computationalType() {
        return TYPE_INSTRUCTION_OFFSET;
    }

    public final String internalType() {
        return String.valueOf(ClassConstants.TYPE_INT);
    }

    // Implementations for Object.

    public boolean equals(Object object) {
        if (object == null || this.getClass() != object.getClass()) {
            return false;
        }

        InstructionOffsetValue other = (InstructionOffsetValue)object;
        if (this.values == other.values) {
            return true;
        }

        if (this.values == null || other.values == null || this.values.length != other.values.length) {
            return false;
        }

        for (int index = 0; index < other.values.length; index++) {
            if (!this.contains(other.values[index])) {
                return false;
            }
        }

        return true;
    }

    public int hashCode() {
        int hashCode = this.getClass().hashCode();

        if (values != null) {
            for (int index = 0; index < values.length; index++) {
                hashCode ^= values[index];
            }
        }

        return hashCode;
    }

    public String toString() {
        StringBuffer buffer = new StringBuffer();

        if (values != null) {
            for (int index = 0; index < values.length; index++) {
                if (index > 0) {
                    buffer.append(',');
                }

                if (values[index] < 0) {
                    buffer.append(values[index]);
                } else {
                    if (isMethodParameter(index)) {
                        buffer.append('P');
                    }

                    if (isMethodReturnValue(index)) {
                        buffer.append('M');
                    }

                    if (isFieldValue(index)) {
                        buffer.append('F');
                    }

                    if (isNewinstance(index)) {
                        buffer.append('N');
                    }

                    if (isCast(index)) {
                        buffer.append('C');
                    }

                    if (isExceptionHandler(index)) {
                        buffer.append('E');
                    }

                    buffer.append(values[index] & 0xffff);
                }
            }
        }

        return buffer.append(':').toString();
    }
}
